Ore flotation process with poly(ethylene-propylene)glycol frothers

ABSTRACT

A process for collecting mineral values from an ore which comprises mixing ground ore with water to form an ore pulp, aerating said pulp in the presence of an effective amount of frother selected from the group consisting of poly(ethylenepropylene) glycols and lower alkyl monoethers of poly(ethylenepropylene) glycols having an average molecular weight in the range of about 150 to about 2,500, each of said frothers being prepared from ethylene oxide and propylene oxide, each of said oxides being employed in amounts of between 5 and 95 mole percent based upon the amount of alkylene oxide reacted and recovering mineral values from the resulting froth.

United States Patent [72] Inventor Robert Ben Booth Stamford, Conn.

[2!] Appl No. 737,811

[22] Filed June 18, 1968 [45] Patented July 27, 1971 [73] Assignee American Cyanamid Company Stamford, Conn.

[54] ORE FLOTATION PROCESS WITH POLYiETI-IYLENE-PROPYLENENLYCOL FRO'IHERS 2 Claims, No Drawings [52] [1.8. CI 209/166 [51] Int. Cl 803d 1/02 [50] Field of Search 209/ 1 66,

[56] References Cited UNITED STATES PATENTS 2,377,129 5/1945 Christmann 209/166 2,797,808 7/1957 Tveter.......... 209/166 2,561,251 7/1951 Van Aardt 209/166 2,950,818 8/1960 Mueller 209/166 2,174,761 10/1939 Schuette 2,677,700 5/1954 Jackson.... 260/615 X 2,965,678 12/1960 Sundberg. 260/615 3,078,315 2/1963 Steele 260/615 3,101,374 8/1963 Putton 260/615 X OTHER REFERENCES Chem. Abstract, 60. 7716 d, 1964.

Primary Examiner-Frank W. Lutter Assistant Examiner- Robert Halper Attorney-John L. Sullivan of poly(ethylene-propylene) glycols having an average molecular weight in the range of about 150 to about 2,500, each of said frothers being prepared from ethylene oxide and propylene oxide, each of said oxides being employed in amounts of between 5 and 95 mole percent based upon the amount of alkylene oxide reacted and recovering mineral values from the resulting froth.

ORE F LOTATION PROCESS WITH POLY(ETHYLENE- PROPYLENIDGLYCOL FROTHERS This invention relates to a method for concentrating minerals from ores by froth flotation. More particularly, the present invention relates to froth flotation processes employing as a frothing agent poly(ethylene-propylene)glycols and lower alkyl mono ethers of such glycols.

Froth flotation is a commonly; employed process for concentrating minerals from ores. In a flotation process, the ore is crushed and wet ground to obtain a pulp. A frothing agent, usually employed with a collecting agent, is added to the ore to assist in separating valuable minerals from the undesired or gangue portions of the ore in subsequent flotation steps. The pulp is then aerated to produce a froth at the surface thereof and the collector assists the frothing agent in separating the mineral values from the ore bycausing the mineral values to adhere to the bubbles formed during this aeration step. The adherence of the mineral values is selectively accomplished so that the portion of the ore not containing mineral values does not adhere to the bubbles. The mineral-bearing froth is collected and further processed to obtain the desired minerals. That portion of the ore which is not carried overwith the froth, usually identifiedas flotation trailings", is usually not further processed for extraction of mineral values therefrom. The froth flotation process is applicable to ores containing metallic and nonmetallic mineralwalues.

ln flotation processes, it is desirable to recover as much mineral values as possible fromuthe ore while effecting the recovery in a selective manner, that is, without carrying over undesirable portions of the ore in'the froth.

While a large number of compounds have foam or froth producing properties, the frothers most widely used in commercial froth flotation operations are monohydroxylated compounds such as C -C,, alcohols, pine oils, cresols and C C alkyl ethers of polypropylene glycols as well as dihydroxylates such as polypropylene glycolssThe frothers most widely used in froth flotation operations are compounds containing a nonpolar, water-repellant group and a single, polar, water-avid group such as hydroxyl (OH). Typical of this class of frothers are mixed amyl alcohols, methylis'obutyl carbinol, hexyl and heptyl alcohols, cresols, tepineol, etc. Other effective frothers used commercially are the C,C alkyl ethers of polypropylene glycol, especially the methyl ether and the polypropylene glycols of l40-2l00 molecular weight and particularly those in the 400-1100 range. In additiomcertain alkoxyalkanes, e.g. triethoxybutane, are used as frothers in the flotation of certain ores.

Although mineral recovery improvements from a preferred frother in the treatment of an ore can be as low as only about 1 percent over other frothers, this small improvement is of great importance economically since commercial operations often handle as much as 50,000 tons of ore daily. With the high throughput rates normally encountered in commercial flota' tion processes, relatively small improvements in the rate of mineral recovery'result in the recovery of additional tons of minerals daily. Obviously then, any frother which promotes improved mineral recovery, even though small, is very desirable and can be advantageous in commercial flotation operatrons.

It is an object of the present invention to provide frothing agents which improve the selective recovery of mineralvalues from ores. It is a further object of the present invention to pro-- vide frothing agents which can be satisfactorily employed in present flotation processes. Furtherobjects of the present invention will become evident in view of the following detailed discussion.

In accordance with the presentzinvention, it has been found that poly (ethylene-propylene) glycols and the lower-mono alkyl C to C carbon atom-ethers of poly(ethylenepropylene )glycols are highly effective frothers.

The frothers of the present invention are added to the ore and intimately mixed therewith either alone or together with a collector prior to and/or during the flotation step. The ore pulp-frother mixture is then treated under conditions to form a froth. The froth selectively removes the mineral values from the ore and the mineral-rich froth is separated from the ore flotation pulp and recovered. This value-depleted pulp which remains in the flotation cell is removed. The mineral-rich froth is then further treated to recover the desired mineral values. In accordance with the process of this invention it has been found that both the amount of mineral values which are recovered and the concentration of mineral values in the froth are substantially increased over prior processes which employ known frothers. These processing improvements are obtained with lower quantities of frothing agents as compared to those used currently in flotation operations. Accordingly, the present invention provides substantial advantages over the prior processes.

The frothers of this invention can be employed in the flotation of metallic and nonmetallic-ores. Exemplary ores which are processed include sulfides and oxides of copper and molybdenum, lead, iron, nickel, cobalt, and'the like. Such ores may also contain precious metal values. Other exemplary ores are phosphate rock, cement rock, glass sands, feldspars, fluorspars, micas, clays, talcs, coals and ores containing tungsten, manganese, sulfur, and water-soluble minerals such as sodium and potassium chlorides, and the like. The frothers of this invention are employed in amounts of from about 0.005 lbs. per ton'ore to about 1.0 lb. per ton' of ore; or preferably from about 0.01 lb. per ton ore to about 0.4 lb. per ton ore. The use of more than about 1.0 lb. per ton ore of the frother generally does not improve recovery sufficiently to economically justify the additional frother cost while the use of less than about 0.005 lb. per ton ore of the frother does not materially improve metal separation.

The frothers of the present invention are methods known to the art.

The poly(ethylene-propylene)gylcols may be prepared by reacting ethylene glycol or propylene glycol with ethylene oxide and propylene oxide. The higher the quantity of ethylene oxide and propylene oxide used, the longer the chain length or the higher the molecular weight of the polymeric glycol obtained.

The C to C monoalkyl ethers of the poly(ethylenepropylene)glycols of the present invention are prepared by reaction of an alcohol with ethylene oxide and propylene oxide and the chain length or molecular weight of the reaction product is dependent on the quantities of the two alkylene oxides used. Typical suitable alcohols are methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, isobutyl, normal amyl, various primary amyl, isoamyl, hexyl'and methylamyl alcohols.

prepared by Primary and secondary alcohols are the preferred alkanol reactants. Also it is preferred to employ normal butanol or isobutanol as the alkanol reactant since the frothers produced therefrom have been found to give improved efficiencies in flotation processes.

The preparation of the frothers'of the present invention is effected in the presence of a catalyst such as alkalies, sodium or potassium hydroxide, amines particularly tertiary amines such as triethanol amine, reaction products of amines and alkylene oxides and also boron trifluoride. The reaction may be carried out sequentially with either the ethylene oxide or propylene oxide being added first or concurrently with the oxides being reacted as a mixture. Reaction temperatures up to 150 C. are employed and pressures up to pounds per square inch are used.

The poly(ethylene-propylene)glycols and mono alkyl ethers useful in the present invention may be characterized in terms of their molecular weights. Products of average molecular weight in the range of about to about 2,500 are suitable for use as frothers with the range of about 250 to about 1,000 being preferred.

The reaction products may be used as flotation frothers as produced, after neutralization with acid or after distillation to remove more volatile fractions. The pure poly(ethylenepropylene)glycols and mono alkyl ethers are useful in the present invention, although the reaction products or mixed fractions also are efficient frothers.

The quantities of reactants are adjusted so that a frother of desired molecular weight may be obtained. For example, a molar quantity of ethylene or propylene glycol or a C to C alcohol is reacted with sufficient ethylene oxide or propylene oxide so that the final polymeric condensate is in the molecular weight range of about 150 to about 2,500. The amount of ethylene oxide to propylene oxide reacted with ethylene glycol, propylene glycol or a lower alcohol may range from mole percent ethylene oxide-95 mole percent propylene oxide to about 95 mole percent ethylene oxide-5 mole percent propylene oxide based upon the total amount of alkylene oxide reacted.

it is an advantage of the present invention that the indicated variations of the quantities of ethylene oxide or propylene oxide or mixtures thereof permit a ready adjustment in the frothing characteristics of the various reaction products. Thus by a change in the ratio of reactants, important factors such as froth volume, bubble structure or froth texture, froth presistency dun'ng flotation or after removal from the flotation machine, selectively, and mineral recovery may be adjusted and controlled to suit the specific requirements of flotation operators in the treatment of various types of ores. Such latitude is not attainable with the frothers used in current flotation practice.

Within the indicated ratio of reactants an increase in the quantity of propylene oxide gives a froth of smaller sized bubbles and of closer knit texture, which is conducive to high recovery ofmineral values in both coarse and fine sizes. An increase in ethylene oxide within the indicated ratio tends to produce a froth of looser texture and larger bubbles, which is conducive to the elimination ofinsolubles from the froth, thus raising the concentrate grade particularly in the flotation of slimey ores.

The frothers of the present invention may be added to the ore pulp prior to and/or during the flotation operation. These frothers may be added directly to the ore pulp or, being soluble and readily dispersed in water, may be prediluted with water and then fed to the ore pulp. Such dilution permits more accurate control of the quantity of frother used and results in decreased frother requirements and lower costs. Stage feeding of the frothers also is frequently advantageous.

The frothers of this invention can be employed either alone or in conjunction with standard frothers and with a conditioning agent or modifier and/or a water-soluble or oily collector or promoter. Suitable water-soluble collectors or promoters which can be employed in the flotation of sulfide or oxide metallic ores are alkali metal xanthates, sodium or potassium ethyl, isopropyl, secondary or isobutyl, amyl, or isoamyl and hexyl xanthates and dithiophosphates such as dicresyl, diethyl, diisopropyl, disecondary or diisobutyl, diamyl or diisoamyl and dihexyl dithiophosphates as free acids or as sodium, potassium or ammonium salts, as well as mercaptobenzothiazole derivatives. Suitable oily collectors which can be employed with the frothers of this invention include dithiocarbamates such as S-allyl-N-ethyldithiocarbamate, S-allyl-N-isopropyldithiocarbamate and S-allyl-N-methyl-dithiocarbamate, as well as allyl xanthates, dialkythionocarbamates and (alkoxycarbonyl) alkyl xanthates; these collectors are oil-soluble.

In the flotation of nonmetallic ores, suitable water-soluble and oil-soluble collectors or promoters are oleic acid, crude and refined tall oil, and tall oil fatty acids, naphthenic acids, the sodium, potassium, and ammonium soaps of such acids, black liquor soap, petroleum sulfonatcs, organic phosphates and polyphosphates, sulfonated oils and fatty acids, sulfosuccinates and sulfosuccinamates. Cationic type collectors such as long chain amines or imidazolines are employed in the flotation ofsilica and silicates and watensoluble minerals.

When collectors are used with the frothers of this invention, they are employed in varying quantities depending on the type of ore treated. For the treatment of the sulfide and oxide ores of base metals, the collector requirement is 0.01 and 2.0 lb./ton of ore, preferably between 0.02 and 0.5 lb./ton of ore. For nonmetallic ores, the collector requirement ranges from 0.05 to 5.0 lb./ton of ore, preferably 0.1 to about 3.0 lb./ton of ore.

Depending on the type of ore treated, conditioning or modifying agents such as alkalies and acids to adjust pH so as to improve selectivity, flotation depressants to inhibit the flotation of unwanted minerals, and activators to enhance flotability and improve flotation rates may be used with the frothers of this invention.

To observe the frothing characteristics of the frothers of the present invention, a laboratory Fagergren flotation machine, operating at about 2100 rpm. with water only in the agitation chamber, is suitable. The frothers are added as 1-3 percent dispersions in water and agitated about 10 seconds with the water, about 2,200 ml. in volume, in the agitation chamber with the air valve closed to simulate a conditioning operation. The air valve is then opened and the froth allowed to build up at the surface of the water so as to permit observation of its volume, structure, and persistency during agitation and after removal from the agitation chamber. Frother dosages of about 0.0050.03 gram usually are sufficient to produce a froth which overflows from the flotation cell.

The following examples illustrate the process of the present invention and are not intended to limit the same. In these examples EO and P0 are used to designate ethylene oxide and propylene oxide respectively and the proportions employed are mole percents.

EXAMPLE 1 Samples of Pennsylvania bituminous coal fines, 600 grams in weight and containing 22.3 percent ash, were conditioned with 1.25 lb./ton fuel oil and varying quantities of frother as given in the following table. Various reaction products of E0 and PO and n-butanol were used as frothers. These reaction products varied in molecular weight and in the ratio of EO and PO used in their preparation. These frothers were compared with technical hcptanol, the frother in standard use in the flotation of this coal. The results obtained in these flotation tests are summarized in the following table.

Frother Coal concentrate Approx. Percent Percent Type mol. wt. Ll)./t0n weight ash Technical heptanol 0. 17 137.3 11. '2 Reaction products of n-butanol with:

5% BIO-05% P0 300-350 0. 011 60. al 1). 0

15% EEO-% lO 300-250 0. 12 68. 2 9. 2

25% -757 PO 400-470 0. 13 6S. 4 0. J

50% TED-50% PO. 550-650 0. 13 G8. 5 .l. l

75 0 EO-25% PO. 1 (100-1.100 0. 14 68. d 0. .3

50% EO-50'ZI. PO 1, 500-1, 800 0. 13 68. 1 0. l

75% ISO-25% PO. 1, 925-2, 100 0. 14 68. l J. 0

50% EO-50% PO 2, 400-2, 500 0. 11 0B. 5 J. l

80 0 EO-20% PO 600-675 0. 12 68. 4 9. 4

J 0 EO-l0% PO. 300-400 0.14 68. 4 J. 5

40% BIO-60% PO 500-550 0. 12 b8. 2 1|. 3

450-550 0. 12 (i8. 1 ii. 1

The results of the above tests demonstrate that alkanol-EO- PO reaction products are effective as frothers over a wide range of molecular weights. Also it is shown that highly effective frothing agents are produced even though the ratio of E0 and PO varies widely in the reaction used to prepare the frothers.

trate contained the major portions of the molybdenum content of the ore which floated simultaneously with the copper minerals. in separate tests, several different frothers were used. The results of these comparative tests are given in the following table.

Concentrate recovery Percent Percent Percent Percent Frother (type) Cu MOS: Cu M052 Triethoxvbutane 24. 53 0. 375 89.39 76. 23 Reaction product.- methyl alcohol with E (moi. t. 250-300) 1 Reaction product: methyl alcohol with P0 (mol. wt. 250-300).. 25. 21 0.381 86. 37 74. 12 Reaction product: meth l alcohol with EO95/,. PO (moi. wt. 250- 300 25. 21 O. 380 89.63 77. Reaction product: n-b and 5% EO-95% PO(mol. wt. 300)... 25. 0.380 89. 91 77. 27 Polypropylene glycol (mol. wt. 425) 25. 10 0.385 86. 23 73. 18

1 Insufficient froth to support concentrate.

gren flotation machine for 3 minutes to produce coal concentrates. Pine oil and methyl amyl alcohol also were used as frothers in separate tests. The recoveries of coal and the ash content of the coal concentrates are given in the following table.

Frother Coal concentrate Percent A pprox. Lh. 'ton Percent ash Type mol. wt. used weight content Pine oil 0. 45 81. 2 15.1 ethyl alcohol.... 0. 45 73.1 14. T Poly(ethylcne'propyiene) glycol from ethylene gl 3'- col with:

5% 130 .159; P0 400 0.30 $1.2 14.2 EO-75% PO. 750 0. 34 81.2 14. 4 50% BIO-50% PO 1, 000 0. 84. 4 14.1 75% EO25% P0. 1.250 0.36 84. 5 1i. 0 110% 150-107; PO 1.500 0. 3.0 14.1 Poly(ethylene-propylene) glycol from propylene glycol with:

5% ED-95% PO 400 0.30 84 4 14.3 40% BIO-% PO. 100 0.33 8-1.6 14. 1 67% E033% PO. 1. 400 0.36 83.5 14. 0 80% PDQ-20% PO 1. 400 0. -11 83. 14. 0

The above results demonstrate the applicability of the poly(ethylene-propylene)glycol frothers of the present invention over a wide range of molecular weights. These frothers achieved higher coal recovery in concentrates of lower ash content than was achieved using larger quantities of the standard pine oil methyl amyl alcohol frothers.

EXAMPLE 3 The above results show that the reaction products of methyl 20 alcohol and n-butyl alcohol with the mixed alkylene oxides gave higher copper and molybdenum recoveries than the standard frothers, triethoxybutane and polypropylene glycol and the reaction products of methyl alcohol with E0 or with P0 alone.

EXAMPLE 5 A copper ore (about 0.80 percent Cu) from the western United States, containing copper values mainly as chalcopy- 30 rite, was ground to minus mesh with 3.3 lb./ton lime, 0.029

35 (MIBC) was used as a frother, while in the other two tests the reaction product of n-butanol was 5 percent EO and 95 percent PO (molecular weight 300) was used as frother. The results of these tests are given in the following table.

Concentrate Frother Cu Type lb./ton Assay Recovery MlBC 0.048 14.97 91.9 EO-PO Reaction Product 0.032 14.77 91.9 MlBC 0.053 16.00 91.69 50 EO-PO Reaction Product 0.053 I630 9316 in the first two tests, identical copper recoveries resultec but the frother requirement with the EO-PO reaction product was two-thirds that of MlBC. Higher copper recoveries were Frother Coal concentrate Percent Approx. Percent ash Type mol. wt. Lb./ton weight content Reaction product: methanol with 25?} PLO-% Po 450 0.12 68. 5 9.1 Reaction product: ethanol with 10?; EO-QOI'} PO... 350 0.10 69.1 9.0 Reaction productt n-propyl alochol with 50".} EO50% PO. 850 0. 13 68. 4 9. 3 Reaction product: iso ropyl alcohol with EOT5% PO 550 0. 12 68. 2 9. 4 Reaction product: iso ntyi alcohol with 5% EEO-% PO.. 550 0. 11 68. 4 9.1 Reaction product: pcntanol-l with 50% BIO-50% PO 900 0.13 68.1 9. 3 Reaction product: isoamyl alcohol with 75% PIC-25% PO.. 1, 000 0. 13 68. 3 9. 2 Reaction product: methyl isobutly carbinol. with 50% -5 0 1, 200 0. 13 68. 5 9. 1

EXAMPLE 4 for l0 minutes to produce a copper concentrate. This concenobtained with the EO-PO reaction product when equivalent quantities of each of the frothers were used in the last two EXAMPLE 6 The copper ore and the procedure used in example 5 were used with the following frothers:

Frother A Poly(ethylene-propylene)glycol from ethylene glycol with 10 percent EO and 90 percent PO (molecular weight about 400) B Poly(ethylene-propylene)glycol from propylene glycol with 10 percent EO and 90 percent PO 1 molecular weight about 450) The metallurgical results obtained are given in the following table and higher copper recoveries were obtained with Frothers A and B.

Concentrate Frother 2 Cu Type lb./tcn Assay Recovery- MIBC 0.048 14.97 91.9 A 0.048 14.93 92.8 B 0048 14.91 93.0

EXAMPLE 7 Concentrate Zinc Type lb./ton Recovery Assay Mixed amyl alcohols 0.32 96.37 41.23 Reaction Product: n-Butanol 0.25 42.25 with percent EO-95 percent P0 (M01. Wt. 300) Reaction Product: n-Butanol 0.27 96.45 42.19 with 50 percent EO-50 percent PO (Mol. Wt. 850) Poly(ethylenc-propylene)- 0.27 96.43 42.24

glycol from Propylene glycol with 10 percent E0 and 90 percent PO (Mol. Wt. 450) The typical frothers of the present invention duplicated the zinc recovery obtained with the amyl alcohol frother, gave somewhat higher concentrate grades. and required lower dosages of frother in the flotation operation.

EXAMPLE 8 A sample ofa lead ore, containing about 1.6 percent Pb as galena, were ground, conditioned 1 minute with 0.042 lb./ton sodium isopropyl xanthate, and floated 5 minutes to produce a lead concentrate. A frother (molecular weight 300) obtained by reacting n-butanol with 5 percent EO and 95 percent P0 was used in the amount of 0.1 lb./ton. A lead concentrate was produced. which assayed 63.05 percent Pb and represented a lead recovery of 93.31 percent. An identical test substituting recovery of 93.25 percent.

EXAMPLE 9 A cement rock from Pennsylvania, containing 69.7 percent CaCO was ground to about percent minus 325 mesh, conditioned with 1.0 lb./ton crude calcium lignin sulfurate, 0.55 lb./ton refined tall oil fatty acids, and 0.10 lb./ton Frother B of example 6 and floated for 5.5 minutes to produce a carbonate concentrate which assayed 82.9 percent CaCO; and contained 91.1 percent ofthe carbonate present in the flotation feed.

A second flotation test was run on this cement rock by the identical procedure except that 0.1 lb./ton of the butanol-EO- PO reaction product of example 5 was used as frother. A carbonate concentrate assaying 83.0 percent CaCO; and representing a carbonate recovery of 90.8 percent was obtained.

This example illustrates the effective use of representative frothers of the present invention in a typical nonmetallic flotation operation.

EXAMPLE 10 A Michigan iron ore, containing about 31.6 percent Fe mainly as hematite associated with a quartz gangue, was ground to about 65 mesh and deslimed. The deslimed fraction was conditioned at 66 percent solids with 2.0 1b./ton sulfuric acid, 1.75 lb./ton heavy fuel oil and 3.2 1b./ton of water-soluble petroleum sulfonates as promoter, diluted to about 20 percent solids and floated for 3 minutes to produce an iron concentrate. After 2.0 minutes of flotation, 0.05 lb./ton of Frother A of example 6 was added to augment the frothing action of the sulfonate promoter and aid in removing the iron minerals. The resulting iron concentrate was cleaned by reflotation to yield a final iron concentrate assaying 62.1 percent Fe and 8.7 percent silica and containing 92.8 percent of the iron present in the feed to flotation.

EXAMPLE 11 A quartz sand containing 0.15 percent Fe O was scrubbed for 2.5 minutes, deslimed and conditioned at 65 percent solids with 0.6 lb./ton sulfuric acid, 1.0 lb./ton ofa 1:1 mixture of oil and water soluble petroleum sulfonate, 0.50 lb./t0n fuel oil and 0.10 lb./ton of the frother used in example 5 and then diluted to about 20 percent solids and floated 2.5 minutes to remove various iron-containing mineral contaminants. The resulting trailing product contained 0.021 percent Fe O and represented 90.2 percent ofthe weight of the flotation feed.

lclaim:

1. A process for collecting mineral values from an ore which comprises mixing ground ore with water to form an ore pulp, aerating said pulp in the presence of an effective amount, as a frother, of a po1y(ethylene-propylene)glycol having an average molecular weight of from about 150 to about 2,500 and having been prepared by reacting ethylene glycol or propylene glycol with ethylene oxide and propylene oxide, the amount of each of said oxides employed in the reaction being between 5 and mole percent based on the total amount of the two oxides employed, and recovering mineral values from the resulting froth.

2. The process of claim 1 wherein the frother is employed in combination with a mineral collector. 

2. The process of claim 1 wherein the frother is employed in combination with a mineral collector. 